Conventionally, a speed change operating device for a bicycle has been well-known which uses front and rear derailleurs to switch a driving chain to a desired one of the multistage front chain gears or rear chain gears for changing the bicycle speed.
Also, the so-called twin lever type speed change operating device has hitherto been well-known which supports first and second operating levers rotatably to one base member through lever shafts to thereby operate the front and rear derailleurs.
Each operating lever generally has a control portion of relatively small width about equal to an axial length of a boss supported to a lever shaft. Therefore, a large space is developed between the control portions of both the lever so that a cyclist operates the first or second lever by independently gripping it by his hand.
Accordingly, his hand operating the lever is unstable, thereby creating the problem that short or excessive operation may cause deterioration of speed change efficiency. Also, the small-width levers may cuase pain in his finger.
A twin lever type speed change operating device has been proposed which has the lever control portions each of larger width than the axial length of the boss. Such device merely widens the utmost end of each control portion, but it is impossible to operate one lever by utilizing the other lever as a basis of operating the one lever. Hence, such twin lever type device, although the pain the cyclist's finger is obviated, is of no effect with respect to improvement in the stability and efficiency for speed change.